Battery charging is an electrochemical process in which the discharged electric energy is replenished from an electric network. The quality of the charging process is critical to the health and longevity of batteries. As such, battery chargers need to be fitted with advanced controls to optimize charging and prolong battery life.
Since batteries are direct current (DC) sources, most battery charging systems in use today employ a power conversion stage that converts the incoming alternating current (AC) power to DC output. FIG. 1 shows a typical single stage high frequency battery charger 100. The typical battery charging system of FIG. 1 receives AC input power from an AC source (not shown). An input rectifier 101 (here an LC filter) converts the input AC into high voltage DC. The input rectifier 101 is followed by a power conversion stage 102 including switching devices 103 (here diodes) and a capacitor 104, a high frequency inverter 105, a high frequency transformer 106, an output rectifier 107 and an LC filtering stage 108 to convert the high frequency AC output into a DC voltage compatible with the battery voltage. Finally, control and sensing circuitry 109, 110, along with a microprocessor 111, are employed to control the charge process and implement the desired charging algorithm, i.e., the rules or parameters by which the battery is to be charged.
Recently, modular charging systems have been proposed where the power stage includes one or more power stages that are operated in parallel to provide DC charging power to the battery. FIG. 2 shows a typical modular charging 200. The charger includes a plurality of modular power stages 201 with associated control circuitry, where each of the modular power stages may have the same architecture as the charger 100 of FIG. 1. However, the power rating of the modular power stages 201 is less than that of a single stage battery charger, as the power rating of the aggregation of the power stages is equivalent to that of the single stage charger. Typically, a controller 202 may provide a data and communication process along with a central microprocessor to control the operation of the power stages 201 and charging process. Further details on such charging configurations are set forth in U.S. Pat. Pub. No. 2004/0189251 to Kutkut et al., which is hereby incorporated herein in its entirety by reference.